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October 01, 2010 (Vol. 30, No. 17)

Improving Assays for Micronuclei Detection

Application of High-Content Analysis System Can Be Beneficial in Toxicity Screening

  • Data-Acquisition Rate

    Click Image To Enlarge +
    Figure 1. Micronuclei formation assay: Following treatment of CHO-K1 cells with 250 µM etoposide and staining with Hoechst 33342, cells were imaged with (A) the large-chip CCD camera or (B) the standard-chip CCD camera. Relative size of images from the two cameras is as shown. Inset: Enlargement of the region of interest outlined in white in (A). Arrow: micronucleus formed at the periphery of a nucleus. Cell count for the standard-chip camera image is 70 for field 1, compared with a cell count of 386 for field 1 for the large-chip camera.

    To maximize the acquisition rate for micronuclei formation assays, a large-chip CCD camera is preferable to the standard-chip size. With a 2,048 x 2,048 pixel array, the large-chip camera acquires a field of view approximately four times that of the standard-chip camera (Table 1 and Figure 1).

    Consequently, fewer fields of view are required to obtain the desired cell count. In addition, capture rates with the large-chip camera configuration are significantly more rapid than with the standard-chip camera in place. Both of these factors contribute to an increased speed of acquisition.

    This is illustrated using dose-response assays with etoposide and mitomycin C as test compounds, with the online cell-count threshold set to 1,000. The number of fields imaged per well to achieve the threshold ranged from 1 to 34 using the standard-chip CCD cameras and 1 to 16 using the large-chip CCD camera.

  • Click Image To Enlarge +

    Use of the large-chip camera reduced plate acquisition times by ~50% compared to those achieved with the standard-chip camera under comparable conditions (Table 1).

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